Where the imperfect has an inflectional nūn among the “five verbs” patterns, jussive formation removes that nūn. In the fourteen-person presentation, seven positions show such endings: three third-person and four second-person positions.
Word / formMeaning / explanation
يَفْعَلَانِ → لَا يَفْعَلَاlet the two men not act.
يَفْعَلُونَ → لَا يَفْعَلُواlet the men not act.
تَفْعَلِينَ → لَا تَفْعَلِيdo not act (one woman).
The dual alif, plural wāw and singular-feminine yāʾ remain; the deleted nūn was inflectional, not one of the root consonants.